Teletypewriter selector magnet

ABSTRACT

A teletypewriter selector magnet, shielded by a housing, has a pair of electromagnets each having a radial airgap, which are mounted below opposed ends of a rotatably mounted armature. An extension of nonmagnetic material is joined to one end of the armature and extends from the housing through a slot formed therein. Shielded conductors are connected to the coils of the electromagnets to selectively energize the magnets and thereby rotate the armature in opposite directions.

United States Patent [7 21 Inventors [2| 1 Appl. No. I 22] Filed [45] Patented [73] Assignee Stuart M. Phelps;

Ernest R. Tudor. both of Rochester, N.Y. 15,113

Feb. 27. 1970 June 15, 1971 The United States of America as represented by the Secretary of the Army [54] TELETYPEWRITER SELECTOR MAGNET 3 Claims, 2 Drawing Figs. [5 2] US. Cl., 335/266, 335/278, 335/281 [51] Int. Cl. n01: 7/13 [50] Field of Search 335/236, 266, 278, 301, 227, 245, 268, 269, 276, 281, 296, l80,l81;10l/93C [56] References Cited UNITED STATES PATENTS 2,458,957 1/1949 335/297X 3,241,006 3/1966 Boyko 335/281 X 3,460,082 8/1969 Stone 335/278 Primary Examiner-G. Harris Attorneys-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and Jeremiah G. Murray ABSTRACT: A teletypewriter selector magnet, shielded by a housing, has a pair of electromagnets each having aradial air gap, which are mounted below opposed ends of a rotatably mounted armature. An extension of nonmagnetic material is joined to one end of the armature and extends from the housing through a slot formed therein. Shielded conductors are connected to the coils of the electromagnets to selectively energize the magnets and thereby rotate the armature in opposite directions.

PATENTED JUN 1 5 I97! FIG. 1

FIG. 2

8 am E mw WM T T S ERNEST R. TUDOR GENT ATTORNEYS TELETYPEWRITER SELECTOR MAGNET The present invention relates generally to improvements in teletypewriters and the like and more particularly 'to a new and improved selector magnet.

In teletypewriter machines, character selection is normally accomplished by means of a high speed lever of armature which moves to one or the other of two limit positions according to an appropriate electrical signal. The electrical signal is applied to a dual-electromagnet device which either directly or indirectly causes the armature to take up the desired position. One of the most critical problems confronting designers of teletypewriter machines which are to be used for secure communications has been the effective shielding of the selector magnet without materially increasing the size and weight of the overall structure.

For example, the mere enclosing of the standard selector magnets in a housing of high magnetic permeability material has resulted in an undesirable increase in the size and weight of the magnets. To simply scale down the magnetic structures will in most cases result in either a prohibitively expensive structure of an unreliable mechanism. Also, reduction in the amount of signal applied to the selector magnet, in order to reduce radiation, may cause malfunctions as a result of incomplete deflections of the armatures. The general purpose of this invention is to provide a new and improved shielded selector magnet designed to reduce to a minimum the amount of stray radiation without causing any of the above mentioned disadvantages. To attain this, the present invention contemplates a unique magnetic structure, wherein the length of the magnetic circuit is minimized, and thereby reduces to a minimum the amount of stray radiation. The magnetic fields incident on the armature are also concentrated at an optimum location to cause a greater torque without any increase in the operating currents.

It is therefore the primary object of the present invention to provide an efiectively shielded teletypewriter selector magnet.

Another object is to provide a highly reliable selector magnet.

Another object of the invention is the provision of a selector magnet having a relatively short magnetic path.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

FIG. 1 shows a front elevation view partly in section of a preferred embodiment of the invention; and

FIG. 2 shows a section of the device takenon the line 2-2 of FIG. 1 looking in the direction of the arrows.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGS. 1 and 2 a selector magnet having a shield 11 and cover 12 of high permeability for enclosing and shielding the magnetic circuit.

A T-shaped support bracket 13 mounted by screws to the backwall 9 of the shield 11 carries a pair of electromagnets 14 and 15 of identical construction. Each of the electromagnets 14 and 15 includes a cylindrical casing 16 having a circular opening 17 in the top wall thereof. A coil 18 is mounted in casing 16 and includes a cup-shaped portion 19 for the reception of a silicon steel pole piece 20, one end of which extends into the opening 17 to form a radial airgap 21. A bolt 22 extends through bracket 13, the bottom wall of housing 16, the axial bore of coil 18, and into a threaded opening in the base of pole piece 20. The casing 16 has a sleevelike extension 16a which projects upwardly around the bolt 22 and the extension 16a forms part of the magnetic circuit.

An armature 23, made of magnetic material, is mounted for rotation on a shaft 24 which is suspended between the wall 9 and cover 12. Armature 23 extends over the airgaps 21 of magnets 14 and 15. Attached to one end of armature 23 is an extension 30 of nonmagnetic material such as brass which passes through a slot 31 formed in the sidewall of shield 11. A

hard steel operating end 33 is mounted on extension 30.

A cable 0 having three insulated conductors 41, 42 and 43 surrounded by a conductive shield 44 passes through an opening in shield 11. Conductive shield 44 is connected to the inside surface of shield 11. Conductor 42 is connected in common to one side of the coils 18 in each of the magnets 14 and 15. The other side of the coils 18 are connected to conductors 41 and 43.

With a signal applied to the conductors 42 and 43, the electromagnet 14 will produce a magnetic field which will be confined generally to the path defined by the dotted lines 50. Opposite north and south magnetic poles are therefore formed on polepiece 20 and the periphery of opening 17 in casing 16 which together will attract armature 23 thereby moving end 33 down.

The magnetic circuit is therefore confined predominantly to the walls of the casing 16 and the polepiece 20. Each electromagnet l4 and 15 when excited will therefore generate a compact magnetic circuit having a magnetic field confined predominantly to a small radial airgap 21 located at extreme ends of the armature. Thus, when an electromagnet 14 or 15 is energized, the resulting magnetic field concentrates in the airgap 21 and exercises an attractive force on the armature 23, which is pivoted and moves rapidly towards the energized electromagnet 14 or 15.

It should be understood that the foregoing disclosure relates to only a preferred embodiment of the invention and that modifications or alterations may be made therein without departing from the spirit and. the-scope of the invention as set forth in the appended claims.

What we claim is:

l. A teletypewriter selector magnet comprising first and second electromagnets; each said electromagnet having outer walls of magnetic material; a radial airgap formed in one of said walls of each said electromagnet; an elongated armature rotatably mounted for rotation about a transverse axis intermediate the ends thereof; and means for mounting said electromagnets with each said airgap spaced slightly below a different one of said ends of said armature for rotating said armature in opposite directions.

2. The device according to claim 1 and further including magnetic shielding means enclosing said electromagnets and said armature.

3. A teletypewriter selector magnet comprising first and second electromagnets; each said electromagnet comprising a cylindrical casing of magnetic material having an axial opening in the top wall thereof, a pole piece mounted along the axis of said cylindrical casing and extending into said opening to form a radial airgap, and a coil mounted in said casing and wound about said axis; an armature having a shaft for rotatably mounting a pair of rigid arms; said airgap of each said electromagnet being mounted immediately below and slightly spaced from the ends of each said arm; an extension of nonmagnetic material attached to the end of one of said arms; said electromagnets and armature being mounted in a housing of magnetic material; said extension extending through a slot formed in the wall of said housing; and conductor means connected from said coils to the exterior of said housing for permitting selective energization of said coils. 

1. A teletypewriter selector magnet comprising first and second electromagnets; each said electromagnet having outer walls of magnetic material; a radial airgap formed in one of said walls of each said electromagnet; an elongated armature rotatably mounted for rotation about a transverse axis intermediate the ends thereof; and means for mounting said electromagnets with each said airgap spaced slightly below a different one of said ends of said armature for rotating said armature in opposite directions.
 2. The device according to claim 1 and further including magnetic shielding means enclosing said electromagnets and said armature.
 3. A teletypewriter selector magnet comprising first and second electromagnets; each said electromagnet comprising a cylindrical casing of magnetic material having an axial opening in the top wall thereof, a pole piece mounted along the axis of said cylindrical casing and extending into said opening to form a radial airgap, and a coil mounted in said casing and wound about said axis; an armature having a shaft for rotatably mounting a pair of rigid arms; said airgap of each said electromagnet beiNg mounted immediately below and slightly spaced from the ends of each said arm; an extension of nonmagnetic material attached to the end of one of said arms; said electromagnets and armature being mounted in a housing of magnetic material; said extension extending through a slot formed in the wall of said housing; and conductor means connected from said coils to the exterior of said housing for permitting selective energization of said coils. 